1. Field of the Invention
The present invention relates to a semiconductor chip and a wiring board wherein external electrodes on both sides of a semiconductor substrate are electrically connected by means of conductive patterns formed so as to follow the sides of the semiconductor substrate and the manufacturing process thereof as well as a semiconductor device that uses the semiconductor chip thereof.
2. Description of Prior Art
In recent years together with the miniaturization and the increased performance of electronics, as represented by computers and communication apparatuses, miniaturization, increased density and increased speed have become required for semiconductor devices. Therefore, a multi-chip type semiconductor device has been proposed wherein a plurality of semiconductor chips are mounted on a wiring board so as to form a module and miniaturization and higher density have been achieved.
In the following, several different modes of conventional semiconductor devices are described.
FIGS. 60 to 64 are cross section views showing conventional semiconductor devices.
First, as shown in FIG. 60, a plurality of semiconductor chips 2 are mounted on a wiring board 1 according to a flip chip system so that electrodes of the semiconductor chip 2 and connection electrodes of the wiring board 1 are electrically connected through metal bumps 3 and a plurality of semiconductor chips are mounted on one wiring board by being arranged in a plane.
Next, as shown in FIG. 61, a plurality of semiconductor chips 5 are layered on a wiring board 4 wherein electrodes of respective semiconductor chips 5 and connection electrodes of the wiring board 4 are electrically connected through metal wires 6 so that the mounting area of semiconductor chips relative to the wiring board becomes smaller in comparison with the mode where semiconductor chips are arranged in a plane.
In addition, as shown in FIG. 62, the surfaces of two semiconductor chips 7 where electrodes are formed are made to face each other and electrodes of respective semiconductor chips 7 are electrically connected through metal bumps 8 so as to have a layered boardless structure.
In addition, as shown in FIG. 63, a plurality of semiconductor devices wherein semiconductor chips 9 are mounted on wiring boards 11 via metal bumps 10 in a flip chip system are layered so that wires of the respective wiring boards 11 are electrically connected through metal bumps 12.
Several different modes of conventional semiconductor devices are described in the above and all of these conventional semiconductor devices implement semiconductor devices formed of a plurality of a semiconductor chips which have a mode wherein a plurality of semiconductor chips are mounted on a wiring board in a plane, a mode wherein a plurality of semiconductor chips are layered on a wiring board, a mode wherein surfaces of semiconductor chips where circuits are formed are made to face each other so as to be electrically connected through metal bumps and a mode wherein mounting bodies formed of semiconductor chips mounted on wiring boards are layered.
In addition, since electrodes are formed only on one side of a semiconductor chip which forms each semiconductor device, semiconductor chips are electrically connected to each other by using metal wires or boards in the case that semiconductor chips are layered.
FIG. 64 is a cross section view of a semiconductor device using a conventional resin wiring board.
As shown in FIG. 64, one, or a plurality, of semiconductor chips 2 are mounted in a plane according to a flip chip system on a resin wiring board 1 formed of a complex material, including an epoxy resin, wherein surface electrodes of the semiconductor chip(s) 2 and connection electrodes on the surface of the resin wiring board 1 are electrically connected through metal bumps 3. Furthermore, connection electrodes on the rear side of the resin wiring board 1 are electrically connected to wires of a mother board 405 by means of solder balls 404. Here, connection electrodes on both sides of the resin wiring board 1 are electrically connected through conductive patterns formed on the inner walls of through holes (not shown) which pass through the inside of the resin wiring board 1.
In this manner, the semiconductor chip(s) 2 is (are) not directly mounted on the mother board 405 but, rather, the resin wiring board 1 is inserted between the semiconductor chip(s) 2 and the mother board 405 in the structure.
However, the respective modes of the conventional semiconductor devices where a plurality of semiconductor chips are layered have the problems as follows.
First, as shown in FIG. 60, since a plurality of semiconductor chips 2 are arranged on the wiring board 1 in a plane, the area of the wiring board 1 needs to be, at least, larger than the sum of the areas of the plurality of semiconductor chips 2 and the larger is the number of mounted semiconductor chips 2, the larger must be the area of the wiring board 1.
In addition, in the semiconductor device shown in FIG. 61, it is necessary to expose electrodes for connecting the metal wires 6 which make an electrical connection with the wires of the wiring board 4 on the upper surface of a semiconductor chip 5 every time that the semiconductor chip 5 is layered and, therefore, the semiconductor chip which is far away from the board becomes small. Accordingly, it is impossible to layer semiconductor chips of the same size and the total length of the metal wires 6 becomes longer when the number of layered semiconductor substrate 5 increases and, therefore, there is a problem that the wire length becomes long.
In addition, in the semiconductor device shown in FIG. 62, it is impossible to layer three or more semiconductor chips 7 and, therefore, there is a limit in the function as a semiconductor device.
In addition, in the semiconductor device shown in FIG. 63, since it is necessary to provide wiring boards 11 between a plurality of semiconductor chips 9, there is problem that the thickness of the semiconductor device becomes large after the layering of the semiconductor chips.
As described above, in the conventional semiconductor devices, the mounting area becomes great in the case that a plurality of semiconductor chips are arranged in a plane, it is impossible to layer semiconductor chips of the same size because of the necessity of providing electrodes for the connection with metal wires, the number of layered semiconductor chips is limited, the functions as a semiconductor device are limited and the thickness of the semiconductor device becomes large due to the structure wherein boards are provided between the layered semiconductor chips and, therefore, it is difficult to achieve miniaturization, improved performance and increased speed.
In addition, the changes in characteristics due to temperature and humidity of a resin wiring board using a complex material, including an epoxy resin, are greater than the changes in the characteristics of a semiconductor chip and, in particular, there is a significant difference in the coefficient of thermal expansion between silicon which is the basic material of a semiconductor chip and an epoxy resin-based complex material and, therefore, a large amount of stress occurs in the connection part between a semiconductor chip and a resin wiring board and, therefore, there is a risk that the connection part will be broken.
Furthermore, since the flatness of a resin wiring board is not of a sufficient degree in comparison with a semiconductor chip, in a flip chip system wherein a semiconductor chip is directly connected to a resin wiring board there is a problem that the electrical connection is not stable between metal bumps formed on the electrodes of a semiconductor chip and connection electrodes of a resin wiring board.
In addition, since the dimension precision of the wires formed on a resin wiring board is not sufficient in comparison with the dimension precision of a semiconductor chip, positional shift occurs in connection parts between the surface electrodes of a semiconductor chip and connection electrodes of the resin wiring board so as to cause a defective connection.
Furthermore, since semiconductor chips are mounted on the resin wiring board in a plane in the structure, it is impossible to make the area of the resin wiring board smaller than the total area of the mounted semiconductor chips and, therefore, there is a problem that the larger the number of mounted semiconductor chips is, the larger the area of the resin wiring board is.
The present invention provides, in order to solve the above described conventional problems, a semiconductor chip of which the main purpose is to prevent the increase in the thickness of the semiconductor device wherein semiconductor chips are layered and in the increase of the board area as well as in the increase of the wire length between semiconductor chips even when a plurality of semiconductor chips are layered on a wiring board and provides a manufacturing process thereof as well as a semiconductor device using this semiconductor chip.
The present invention provides a wiring board using silicon as a material of the wiring board and a manufacturing process thereof in order to solve the above described conventional problems.